While we are often encouraged to have concern for our cholesterol levels, it is seldom mentioned that one of the two main forms of cholesterol - known as high density lipoprotein (HDL) cholesterol - is associated with a reduced risk of cardiovascular disease consequences, such as heart attacks and stroke. Also, while cholesterol reduction with commonly used statin drugs can reduce the risk of heart attack, recent evidence published in the journal Circulationfound that this benefit does not extend to individuals with relatively high levels of HDL cholesterol in their bloodstreams. This research supports the notion that an individual's total cholesterol level may not be particularly useful for determining whether they are a heart attack waiting to happen.

The evidence as it stands suggests that boosting HDL cholesterol levels in the body is a sensible strategy for those looking to reduce their risk of cardiovascular disease. From a nutritional perspective, eating more fish rich in omega-3 fats, such as salmon, mackerel, herring and sardine, appears to have the ability to raise HDL cholesterol levels. However, oily fish is not the only food that has potential here: in a study published recently in the journal Angiology, individuals who ate 20g of walnuts each day for eight weeks enjoyed satisfying increases in their HDL cholesterol levels.

This is not the only evidence that suggests that cracking into walnuts over the festive season might have benefits for the heart. Another study, published in the European Journal of Clinical Nutrition in 1998, found that walnut eating led to substantially enhanced HDL levels. Other studies have found the consumption of walnuts has the capacity to bring down overall cholesterol levels. The findings are supported by other work which has found that regular nut eating is associated with a significantly reduced risk of cardiovascular disease. While it is not clear whether walnuts have any distinct nutritional benefits over other nut types, one thing that is relatively unique to them is their high content of a fat known as alpha-linolenic acid (ALA). This fat belongs to the socalled omega-3 family to which fish oils belong.

While ALA is not precisely the same as the fats found in fish, it appears nonetheless to have some effects in the body that would be expected to reduce the risk of cardiovascular disease, including the ability to thin the blood. Also, like the omega-3 fats found in oily fish, high ALA consumption has been linked with a reduced risk of cardiovascular disease. The science suggests that the walnut is one festive food that we can eat to our heart's content.

Dear John

I am 33 and experience very tender and swollen breasts for 10 to 14 days before my period. My doctor recommended evening primrose oil - I take 1g a day. This helped for a while, but now my symptoms are as bad as before.
Kat

Clinical experience and some evidence shows that evening primrose oil can be useful in the treatment of breast pain. It seems that the effective dose is somewhere between 2-4g per day. You might like to try increasing the dose, though it may take two or three cycles before the full effect of any increase in the dose is seen. Many natural health practitioners believe that breast pain and swelling in the premenstrual phase is a sign of a relative excess of the sex hormone oestrogen at this time. Other symptoms suggestive of this hormonal imbalance include general fluid retention and mood change (irritability). In my experience, the herb Agnus castusis usually highly effective in relieving these symptoms. This remedy is believed to help restore hormonal balance in pre-menstrual phase. I suggest you take 40 drops of tincture (alcoholic) in water each morning.

· If you have any issues you would like Dr Briffa to address in his column, please email him on john.briffa@observer.co.uk. Please note that Dr Briffa cannot enter into any correspondence. You can also visit www.drbriffa.com. Before following any recommendations in this column, you should consult your own medical adviser about any medical problems or special health conditions

Nutrition news

Some parents will be concerned about the amount of pesticides that make their way into their children's bodies from their diets, and may opt for more organic produce as a result. In a recent study published in the journal Environmental Health Perspectives, researchers in the US assessed whether a switch to organic food makes any appreciable difference in the levels of pesticide residues in children.

Urine samples of 23 children were tested for the presence of the residues of two common pesticides of the organophosphate type (malathion and chlorpyrifos) over a 15-day period. For the first three and final seven days of the testing period, children ate their normal diet. During the five days in between, children's normal diets were mostly substituted for organic foods.

The researchers found that during the five days when the children were eating a mainly organic diet, levels of the residues of the two pesticides tested fell from significant to non-detectable levels. Levels were found to rise immediately again on the reintroduction of the conventional diet. The authors of this study concluded that eating an organic diet led to dramatic and immediate protection from pesticide exposure and is likely to have health benefits in the long term.